Contrary to popular belief, toads do not typically produce the deep, resonant “croak” commonly associated with their close relatives, the true frogs. Instead, these amphibians vocalize through a variety of trills, chirps, and buzzing sounds, often characterized by a more sustained and melodic quality. Although both frogs and toads belong to the order Anura, their sound production and the context in which they vocalize differ significantly.
The Variety of Toad Vocalizations
Toad calls are distinct from the lower-pitched, smoother vocalizations of many true frogs. The American toad, for instance, produces a long, high-pitched musical trill that can last anywhere from six to thirty seconds. This sustained sound is often described as a drawn-out, warbling “rrrrrr” sound, which is characteristic of the species.
The common toad, a species found in Europe, creates a higher-pitched and starker sound, often sounding like a rough ‘qwark-qwark-qwark’. This call differs from the low-pitched, repetitive croak of the common frog. The Natterjack toad has a very raspy and high-pitched call that carries over long distances, sometimes heard up to two kilometers away.
Beyond these mating songs, toads also produce other sounds, including chugs, chirps, and nasal wails. The specific characteristics of pitch, duration, and rhythm are unique to each species, allowing individuals to recognize their own kind. This specificity ensures that males only attract and breed with females of the correct species.
The Purpose of Toad Calls
Toad vocalizations serve several specific functions, primarily executed by males. The most frequent and loudest sound is the advertisement call, or mating call, used to attract females to breeding sites. Male toads congregate in a chorus near water bodies, competing to have their calls heard by potential mates.
Females are drawn to these nightly choruses, assessing a male’s quality based on the characteristics of his call, such as duration and frequency. The energy expenditure required to produce these loud, long calls is substantial. The calls are an honest signal of the male’s health and readiness to reproduce.
Another vocalization is the release call, a short, distinct sound a male makes when mistakenly grasped by another toad. Since only males typically vocalize to attract mates, this call acts as a defensive signal to indicate its sex, causing the other toad to let go. Toads also utilize territorial or aggressive calls to warn off competing males who encroach on a defended space.
The Biology of Sound Production
The mechanism for sound creation in toads is a specialized physiological process involving air movement and vibration. The sound originates when the toad forces air from its lungs, through the larynx, and across its vocal cords. These folds of tissue vibrate as the air passes over them, producing the initial sound.
This raw sound is then amplified and modulated by the vocal sac, a thin-walled pouch located under the toad’s throat. The vocal sac inflates with air from the lungs, acting as a resonator to project the sound outward. Toads and frogs produce repeated vocalizations without taking a new breath by moving air between the lungs and the vocal sac.